As a safety precaution, all-terrain vehicle (ATV) transmissions often include an engine speed limiter for reverse and neutral operation. Some of these “rev limiters” function by controlling ignition timing and spark upon reaching a predetermined engine speed or number of revolutions per minute (rpm). For example, if the ATV is in reverse and 4500 rpm are reached, the rev limiter will cut the engine ignition timing to maintain the speed at or below the predetermined set point of 4500 rpm. Rev limiter override switches have also been added so the user can switch off the rev limiter in situations where more power in reverse is needed. Such situations may include when the ATV is stuck or when backing up a steep ramp into a vehicle.
However, with more powerful ATV engines being used a problem occurs that the through-engine drive shaft flexes under heavy reverse rotation loads as the right angle helical cut gear transfers power from the engine transmission. The driven gear tends to climb the drive gear that is secured to the drive shaft as the shaft flexes. This causes the teeth to misalign and break. Another situation occurs when the ATV moves from a slippery surface where the wheels are spinning to a higher traction surface where the wheels stop spinning as freely and the load suddenly increases. This can also cause gear teeth misalignment and breakage within the engine.
A more robust gear system, less susceptible to breakage is needed for high torque engines. Such a system should not add excessive weight or cost to the engine.